1. Field of the Invention
The present invention relates to an airbag apparatus for a front passenger seat for protecting a passenger sitting in the front passenger seat upon collision of a vehicle, such as a car, to thereby ensure safety of the passenger. More particularly, the invention relates to a reinforcement structure for a fracture-opening section which is formed in an instrument panel cover (hereinafter referred to as an xe2x80x9cinterior coverxe2x80x9d) in opposition to an airbag and which breaks so as to allow unfolding and expansion of the airbag.
2. Description of the Related Art
An airbag apparatus for a front passenger seat of a vehicle, such as a car, basically includes an airbag, an airbag case for accommodating the folded airbag, and an inflater for inflating the airbag. In addition, such an airbag apparatus includes a closure plate which is attached to an opening which is formed in an interior cover in opposition to an opening portion of the airbag case, or a fracture-opening section which is formed in the interior cover and which fractures from a fragile portion so as to separate from the interior cover.
Generally, the instrument panel of an automobile consists of an instrument panel core formed from a synthetic resin, such as polypropylene, and an interior cover, which covers the instrument panel core and is formed of a synthetic resin, such as polypropylene.
Japanese Patent Application Laid-Open (kokai) No. 7-172256 discloses an airbag apparatus for a front passenger seat in which an opening is formed in an interior cover, and a closure plate is attached to the opening. Further, in Japanese Patent Application 11-117972, the assignee of the present application has proposed an airbag apparatus for a front passenger seat which has a fracture-opening section formed in an interior cover. Specifically, through application of a laser beam, a fragile contour portion and a fragile center splitting portion are formed to thereby define the fracture-opening section, such that the fracture-opening section can be divided into first and second subsections. First and second reinforcement plate members are fixedly attached to back surfaces of the first and second subsections. Each of the first and second reinforcement plate members has a hinge portion and a bent leg portion. The leg portions of the first and second reinforcement plate members are engaged with hooks fixed to the front and rear walls of an opening portion of an airbag case. Upon inflation of the airbag, the contour portion and the center splitting portion are broken, so that the fracture-opening section opens apart from the interior cover.
FIG. 1 shows a former conventional airbag apparatus for a front passenger seat. The airbag apparatus for a front passenger seat is disposed under a horizontal plane 10a of an interior cover 10 located in the vicinity of a windshield 1a of a vehicle. The airbag apparatus includes an airbag case 12 having an opening portion 12a formed in opposition to the back surface of the interior cover 10. An airbag 11 is accommodated within the airbag case 12 in a folded state, and is inflated by means of gas from an inflater. An opening lid 13 formed of a flexible synthetic resin is disposed at an opening portion 10b formed on the interior cover 10 in opposition to the opening portion 12a of the airbag case 12. Upon inflation of the airbag 11, grooves 13a and 13bxe2x80x94which are formed along the centerline of and along the periphery of the opening lid 13 and serve as fragile portionsxe2x80x94are broken, so that the opening lid 13 is split into two fracture pieces, which open apart in opposite directions toward the front and rear of the vehicle, respectively. The inflating airbag 11 projects outward through the thus-formed opening.
A mounting leg portion 14 and a plurality of engagement pieces 15 are integrally formed on the back surface of the opening lid 13. The mounting leg portion 14 assumes the form of a rectangular frame slightly greater in size than the opening portion 12a of the airbag case 12. The engagement pieces 15 are elastically engaged with the edge of the opening portion 10b of the interior cover 10. A plurality of rectangular through-holes 14c are formed in front and rear walls 14b of the mounting leg portion 14. When the opening lid 13 is fitted to the opening portion 10b of the interior cover 10, the rectangular through-holes 14c are engaged with corresponding hooks 16 fixed to front and rear walls 12b of the opening portion 12a of the airbag case 12 and to a rear wall 12b of the opening portion 12a of the airbag case 12.
When the airbag 11 inflates, through fracture along the grooves 13a and 13b formed along the centerline of and along the periphery of the opening lid 13, the opening lid 13 is split into two fracture pieces, which open apart in opposite directions toward the front and rear of the vehicle, respectively. Since the rectangular through-holes 14c formed in the front and rear walls 14b of the mounting leg portion 14 are engaged with the hooks 16 of the airbag case 12, scattering of the fracture pieces of the opening lid 13 is prevented.
FIGS. 3A and 3B show the latter airbag apparatus for a front passenger seat.
FIG. 3A is an enlarged partial view of the airbag apparatus in which a fragile contour portion 21a and a fragile center splitting portion 21b are formed in a single-layer interior cover 20 along a fracture line 21. FIG. 3B is a cross-sectional view taken along line IIIBxe2x80x94IIIB in FIG. 3A.
The contour portion 21a and the center splitting portion 21b are formed on the interior cover 20 by means of a laser. Specifically, a pulsating laser beam from a laser is applied to the interior cover 20 from behind while being moved relatively along the outline edges of reinforcement plate members 25a fixed to the back surface of the interior cover 20. Thus, perforations 23 are formed in the interior cover 20 along the fracture line 21 to thereby form the contour portion 21a, which has a size corresponding to the size of an opening portion 22a of an airbag case 22. Similarly, the center splitting portion 21b is formed. Upon inflation of an airbag 26, the contour portion 21a and the center splitting portion 21b are broken. As a result, the fracture-opening section is split into front and rear subsections 27a and 27b, which are then turned inside out. Subsequently, the inflating airbag 26 projects outward from the interior cover 20 through the thus-formed opening, and protects the passenger from the impact force of collision.
The thus-configured automobile airbag apparatus functions in the following manner. Upon collision of the vehicle, an impact force caused by the collision is detected by a sensor. A control unit including a CPU judges whether or not the detected impact force is equal to or higher than a predetermined value. When the control unit judges that the impact force is not lower than the predetermined value, the control unit issues a signal for causing the inflater to generate a predetermined gas. The gas is fed to the airbag so as to promptly inflate the airbag.
In the conventional airbag apparatus for a front passenger seat shown in FIG. 1, the opening portion 10b is formed in the interior cover 10 in such a manner as to face the opening portion 12a of the airbag case 12. The opening lid 13 is a discrete element different from the interior cover 10 and made of a flexible resin material and is fitted into the opening portion 10b. Thus, the manufacture and assembly work of the interior cover 10 and the opening lid 13 are rather complicated. Also, when an external force is applied to the opening lid 13, the opening lid 13 easily deforms when an external force is applied thereto, with possible breakage of the groove 13a formed at the center of opening lid 13, thereby damaging the appearance or design of the interior cover 10.
Also, in the case of the airbag apparatus for a front passenger seat shown in FIGS. 3A and 3B, the perforations 23 for the contour portion 21a and the center splitting portion 21b are formed on the interior cover 20 through laser processing. Therefore, the perforations 23 perpendicularly penetrate the interior cover 20 from the back surface to the front surface thereof.
As a result, the contour portion 21a and the center splitting portion 21b are weak against an external pressure (load). Therefore, if a passenger accidentally places his/her hand or arm on the fracture-opening section, the center splitting portion 21b may break and subside easily.
Further, since the perforations 23 perpendicularly penetrate the interior cover 20 from the back surface to the front surface thereof, upon breakage of the fracture-opening section, the contour portion 21a and the center splitting portion 21b form a saw-blade-like cut surface along the fracture line 21. As a result, sharp edges are formed on the wall surface of the opening, which is undesirable from the viewpoint of safety.
An object of the present invention is to solve the above-mentioned problems in the existing airbag apparatus for a front passenger seat and to provide an airbag apparatus for a front passenger seat which has reinforcement means for enabling a fracture-opening section to sustain external pressure and which provides improved appearance and safety.
In order to achieve the above-object, the present invention provides an airbag apparatus for a front passenger seat built in an instrument panel of a vehicle. The airbag apparatus comprises an airbag case accommodated within a core of the instrument panel and having an opening portion located in opposition to a back surface of a cover of the instrument panel; an airbag accommodated within the airbag case in a folded state, the airbag being able to be inflated by means of gas from an inflater; a fracture-opening section defined in the cover to be located in opposition to the opening portion of the airbag case, the fracture-opening section having a fragile contour portion surrounding the fracture-opening section and a fragile center splitting portion for dividing the fracture-opening section into front and rear subsections; front and rear reinforcement plate members fixedly attached to back surfaces of the front and rear subsections, each of the front and rear reinforcement plate members being connected to the opening portion of the airbag case via a hinge portion; and reinforcement means provided at mutually-opposed end portions of the front and rear reinforcement plate members and adapted to reinforce the center splitting portion.
The airbag apparatus of the present invention can be manufactured easily. Further, the fracture-opening section can be fractured reliably along the contour portion and the center splitting portion. Since the center splitting portion can sustain external pressure applied onto the upper surface of the interior cover, the fracture-opening section does not deform or subside. Therefore, the airbag apparatus of the present invention provide an improved appearance and safety.
Further, since the front and rear subsections of the fracture-opening section are connected reliably by the reinforcement plate members before being separated from the interior cover along the contour portion and the center splitting portion upon expansion of the airbag, the front and rear subsections do not scatter, and no sharp edges are formed on the wall surface of the opening extending along the fracture line.